50-ohm line receiver design help?

Thread Starter

lindula

Joined Sep 23, 2016
76
Hello, I want to use the MAX4222 as a 50-line driver what would I use as a receiver at the other end of the cable?



Thanks,
Joe
 

Papabravo

Joined Feb 24, 2006
14,862
Hello, thank you for responding to my post. The Max4222 is single-ended output.

Would I need a single-ended input device, would an op-amp work?

Thanks,
Joe
You can still use a line receiver with a reference at Vcc/2 and a 50 Ω termination resistor.
 

Papabravo

Joined Feb 24, 2006
14,862
Would I wire it up like in Figure 6a?
No, that would not be a 50Ω system. Why would you need a quad part? Wouldn't a single receiver be a better choice? Last time I did this was 3 decades ago and I used a 26LS32, which was a quad part, but then I had 4 lines in the design. Don't know if they make that part any more. Don't know what your budget is or what kind of signals you are using the 50Ω driver for. To make a 50Ω system, you need a cable with a 50Ω characteristic impedance, a driver with a source impedance of 50Ω and a 50Ω termination at the receiver end. The two 50 Ω resistors are like a voltage divider that will cut your signal amplitude in half, so having some gain in the driver might be a good idea. Lotta variables here, are you sure you have the design chops to do this?
 

Thread Starter

lindula

Joined Sep 23, 2016
76
No, that would not be a 50Ω system. Why would you need a quad part? Wouldn't a single receiver be a better choice? Last time I did this was 3 decades ago and I used a 26LS32, which was a quad part, but then I had 4 lines in the design. Don't know if they make that part any more. Don't know what your budget is or what kind of signals you are using the 50Ω driver for. To make a 50Ω system, you need a cable with a 50Ω characteristic impedance, a driver with a source impedance of 50Ω and a 50Ω termination at the receiver end. The two 50 Ω resistors are like a voltage divider that will cut your signal amplitude in half, so having some gain in the driver might be a good idea. Lotta variables here, are you sure you have the design chops to do this?
Always learning something new. No budget constraints. Just trying to do design a receiver circuit to the driver circuit.

I'll keep trying. Thank you for taking the time to respond to my message.

Respectfully,
Joe
 

Papabravo

Joined Feb 24, 2006
14,862
As you search for
Always learning something new. No budget constraints. Just trying to do design a receiver circuit to the driver circuit.

I'll keep trying. Thank you for taking the time to respond to my message.

Respectfully,
Joe
As you search for a suitable part keep in mind that there are parts out there for applications that may have nothing to do with what you are up to. For example there are LVDS parts which are used in high speed Low Voltage Differential Signaling. These may or may not work for you. There are also RS-485/RS-422 Receivers/transceivers, which again may or may not work for you. I was unable to find a single version (as opposed to a quad) of the 26LS32 which electrically should be a good place to start. There are also a family of parts from TI with numbers like 75xxx which are called line drivers and receivers. Finally Maxim apparently has companion receivers to the MAX4222. Whatever you find check back with us and show us a schematic of what you are planning including the length and characteristics of your cable, and the frequencies of interest in the transmitted signal.

EDIT: Depending on what the receiver output is connected to you may be able to use the driver chip as the receiver. One input is connected to the cable and a 50Ω terminating resistor to ground. Connect the other input to a suitable reference between ground and Vcc. Connect the transmitter according to Figure 1a in the datasheet.
 
Last edited:

Thread Starter

lindula

Joined Sep 23, 2016
76
Papabravo,

Hello, thank you very much for responding to my messages. I appreciate your time in explaining things so my project will work. You mentioned that there is a companion part to the Max4222, is that a Max4444?

Thank you,
Joe
 

Papabravo

Joined Feb 24, 2006
14,862
Papabravo,

Hello, thank you very much for responding to my messages. I appreciate your time in explaining things so my project will work. You mentioned that there is a companion part to the Max4222, is that a Max4444?

Thank you,
Joe
That is the one.
 
Top